Remove usage of base::ObserverList<T>::Iter::GetNext() in //content.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index b13d2ca3640dfca90cc8cb9b5a984e3e022fee36..348f57da7bff23781c8704f4fb9fb3bf66a4aae0 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -1506,10 +1506,8 @@ bool RenderFrameImpl::OnMessageReceived(const IPC::Message& msg) {
   if (!frame_->document().isNull())
     GetContentClient()->SetActiveURL(frame_->document().url());
 
-  base::ObserverListBase<RenderFrameObserver>::Iterator it(&observers_);
-  RenderFrameObserver* observer;
-  while ((observer = it.GetNext()) != NULL) {
-    if (observer->OnMessageReceived(msg))
+  for (auto& observer : observers_) {
+    if (observer.OnMessageReceived(msg))
       return true;
   }